Prefilters/Postfilters

Prefilter and postfilter plugins are very similar in concept; where
they differ is in the execution -- more precisely the time of their
execution.

string smarty_prefilter_name (string $source, object &$smarty)

Prefilters are used to process the source of the template immediately
before compilation. The first parameter to the prefilter function is
the template source, possibly modified by some other prefilters. The
plugin is supposed to return the modified source. Note that this
source is not saved anywhere, it is only used for compilation.

string smarty_postfilter_name (string $compiled, object &$smarty)

Postfilters are used to process the compiled output of the template
(the PHP code) immediately after the compilation is done but before the
compiled template is saved to the filesystem. The first parameter to
the postfilter function is the compiled template code, possibly
modified by other postfilters. The plugin is supposed to return the
modified version of this code.